1. Field of the Invention
The present invention relates to a buffer attached to a bottom of a sprocket to decrease a noise and a shake/vibration occurring in a chain driving system, and more particularly, relates to a sprocket buffer for a chain gearing mechanism wherein a pin portion to be inserted to a coupling hole of a sprocket is improved so as not to be cut off, the sprocket buffer being an elastic band type that is positioned to adhere closely along a surface of a sprocket bottom.
2. Description of the Prior Art
As shown in FIG. 1, a conventional chain gearing mechanism comprises a driving sprocket 1a, a driven sprocket 1b and a chain 2 to connect the sprockets, wherein the driving sprocket 1a rotates the driven sprocket 1b by transferring power through the chain 2. The conventional chain gearing mechanism has a merit that significant power can be transferred by maintaining a constant speed ratio, whereas it has a problem that a noise and a shake/vibration are terrible. Since metal to metal surfaces are facing each other, such a structure continuously produces noise, shake and vibration. Specifically, in a case when chains and sprockets are worn according to increased use, the noise is more loudly produced because of unfit engagement.
In order to solve and improve the problem of the conventional chain gearing mechanism, there has been provided a pin type buffer 4 which is inserted in a coupling hole 3a formed on the tooth bottom surface of a sprocket, as shown in FIG. 2. When the pin type buffer 4 is inserted in the coupling hole 3a, a head 21 of the buffer is kept upwardly projected by about 2-3 mm from a bottom 3 of the sprocket. Further, when the sprockets 1a, 1b are connected to a chain roller 6, the pin type buffer 4 performs the role of buffering such that the chain roller 6 and sprockets 1a, 1b do not directly collide with the pin head 21 being pressed by the chain roller 6. However, the conventional chain gearing mechanism may result in an inaccurate engagement caused by a non-straight or a misalignment of the sprockets 1a, 1b and the chain 2 due to an outer and inner circumstances, to an error occurrence in a pitch, and/or to other error occurrences due to a wearing-out of the chain 2 and sprockets 1a, 1b. As illustrated in FIG. 3, in a chain driving, if the chain roller 6 changes a phase status to a portion B rather than a portion A located at a front center of the bottom 3 of the sprockets 1a, 1b, the pin type buffer 4 is biased to the portion B, thereby causing louder noise, shake, and vibration.
Accordingly, the conventional chain gearing mechanism has a problem of noise and shake/vibration caused during the process that the sprockets 1a, 1b are engaged with the chain 2 due to a fact that all the materials are metal, and furthermore, such problem still exists in the case where the pin type buffer 4 is provided to reduce the noise, shake and vibration.
When the pin type buffer 4 is junctioned to the bottom 3 of the sprockets 1a, 1b, even if the chain roller 6 starts to be junctioned at the portion A, which is an accurate engagement position, it collides against the bottom 3 around the portion B after first making contact with the pin type buffer 4, thereby generating a noise and a shake/vibration of the collision. Furthermore, the occurrences of a non-straight or a misalignment of the sprocket 1a, 1b and the chain 2 due to general outer and inner circumstances, to errors by the pitch, and/or to an old chain 2 and old sprockets 1a, 1b, will result in an inaccurate engagement of the chain roller 6 with the bottom 3 of the sprockets 1a, 1b. In this event, as a collision starts not from the buffer 4 where the chain roller 6 is connected to the bottom 3 of the sprockets 1a, 1b but from the bottom 3 of other portions, there is no effect of reducing the noise and the shake/vibration caused by the collision. Rather, in a case where a large compressive force is received from the chain roller 6, the pin type buffer 4 is compressed to be inserted into the coupling hole 3a and therefore, makes contact with the chain roller 6 and the bottom 3 of the sprockets 1a, 1b, thereby generating the noise and the shake/vibration of the collision.
To solve the above-indicated problems, as illustrated in FIG. 4, there has been provided a band-type buffer 5 to buffer an impact throughout a whole bottom 3, comprising an elastic band 10 to cover the whole bottom 3 of the sprockets 1a, 1b; a cylindrical pin 20 for being fixedly inserted into a coupling hole 3a formed in the bottom 3, which is coupled with a lower part of the elastic band 10; and a reinforcement rim 30 formed in one body on an outer peripheral surface of the pin 20 in the lower end of a pin head 21 to support the portion where the elastic band 10 and the pin 20 are coupled, the pin head 21 being upwardly projected as long as a determined length.
However, the band-type buffer 5, wherein the reinforcement rim 30 corresponding to a neck portion of the pin is adhesively inserted into the coupling hole 3a, has a defect that a life of the buffer is short because the elastic band 10 and the pin 20 are cut off by a repeated application of shear force toward the neck portion of the pin if the chain roller 6 is biased in any one direction upon a chain driving.
Accordingly, an object of the present invention is to solve the problems by providing a sprocket buffer for a chain gearing mechanism that extends the buffer's life by preventing any cut-offs which may occur by a shear force applied to the neck portion of the pin when making contact with the chain roller.